• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.12 no.2
• /
• pp.48-48
• /
• 1976

• Applied Chemistry for Engineering
• /
• v.2 no.2
• /
• pp.185-191
• /
• 1991

The chemical composition and characteristics of the source rock collected from Dolgorae-1 well in Korea continental shelf block VI( $35^{\circ}$ 18'N.L., $130^{\circ}$ 28'E) have been investigated. An oil show analyzer(OSA) has been used to determine the contents of gas, oil and total organic carbon(TOC). The average TOC value for the sample is found to be 0.59%. The OSA has also provided hydrogen index and $T_{max}$, the maximum temperature which generate maximum hydrocarbons from kerogen. From a $T_{max}$-hydrogen index diagram the type of organic matter in the source rock was estimated to be type III kerogen. The content of bitumen and its molecular weight have been determined by means of extraction method and gel permeation chromatograph, respectively. The physicochemical properties has been studied using X-ray diffraction spectrometer, IR spectrometer and thermogravimetric method. On the basis of the results obtained in the present work, the samples collected from Dolgorae-1 well are evaluated to be poor source rocks.

• The Journal of the Acoustical Society of Korea
• /
• v.37 no.6
• /
• pp.404-411
• /
• 2018

This paper proposes a dolphin whistle mimicking underwater communication method using FSK (Frequency Shift Keying) and method to improve BER (Bit Error Rate) performance by using multipath gain combining. The proposed method divides whistle sound into short time intervals and transmits FSK modulated signal that ensures orthogonality of the symbol. Multipath gain can be obtained by using characteristic of mimicked signal frequency that varies with time. To demonstrate the performance of the proposed method, computer simulations and lake experiments were conducted. Computer simulation results show that an additional multipath gain is obtained by multipath. From lake experiments, when symbol length is 20 msec and modulation band is 900 Hz, the proposed FSK method with multipath combining gain obtains BER of 0.002, which is better than CSS (Chirp Spread Spectrum) with BER of 0.185. he proposed based on FSK method has higher imitation degree than the CSS method by analyzing mean cross-correlation value in the time - frequency domain of the imitated signal and actual whistle signal.

• Proceedings of the Korean Aquaculture Society Conference
• /
• 2006.05a
• /
• pp.59-60
• /
• 2006

• Proceedings of the Korean Society of Fisheries Technology Conference
• /
• 2002.05a
• /
• pp.83-84
• /
• 2002

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.38 no.4
• /
• pp.271-277
• /
• 2002

This paper was described on the characteristics of bottlenose dolphin (Tursiops truncatus) whistle to develop a warning and attracting acoustic system which can be made friends woith environment and minimized to the fishing pollution from Cetaceans. The experiment for the acoustics of bottlenose dolphin whistle was carried out in dolphin performance hall at Seoul Grand Park during 18th~19th April, 2002. The frequency and the spectrum level of whistle a same pool were revealed 6~10KHz and 85㏈ but those revealed two harmonic waves a 6.7KHz and 21.3KHz for the frequency and 110㏈ and 94㏈ for the spectrum level, respectively, when a dolphin isolated from others. The range of frequency change of whistle was 3.86KHz and continuous time was 0.08 sec. The range of frequency change 10.20 KHz higher as 14.06 KHz and continuous time was 0.11sec longer as 0.19sec when a dolphin isolated from others. By the Mann-Whitney test for the result, there was a significant difference for the range of frequency change and continuous time between normal condition and when a dolphin was isolated from others. The pattern of whistle at the dolphin performance hall was five types and the frequency was getting increased slowly in the range of 5~10KHz at normal condition but there were pattern change of 5~20KHz at the isolated condition. Therefore it is thought that these experiments would be valuable for the development of acoustic system.

• Geophysics and Geophysical Exploration
• /
• v.18 no.2
• /
• pp.39-53
• /
• 2015

Analysis of multi-channel seismic reflection profiles acquired from the southwestern margin of Ulleung Basin reveals that the cut and fill structures, which show U-shaped or V-shaped morphology, occur on variable size. The cut and fill structure mostly consists of fine-grained sediments on the well data and is characterized by transparent or semitransparent seismic facies on the seismic section. Such cut and fill structures dominantly occur in the syn-compressional megasequence (MSQ3), which was deposited during basin deformation of late Miocene, among the four megasequences of the study area. These cut and fill structures can be divided into three groups based on their size and formation time. The cut and fill structures of Group I were formed when Dolgorae structure was active, and occurred on a small scale. The cut and fill structures of group II were formed when both Dolgorae structure and Gorae V structure were active, and the number and size of those increased compared with group I. The cut and fill structures of group III were formed when Dolgorae structure was weaken gradually but Gorae V structure kept active, and the number and size of those decreased in comparison with group II. Consequently the cut and fill structures in the southwestern margin of Ulleung basin are interpreted as submarine canyon based on spatial distribution, size and fill sediment. They were controlled by the tectonic movement in response to basin closure and tectonic-induced sediment supply variation.

• Geophysics and Geophysical Exploration
• /
• v.26 no.3
• /
• pp.126-137
• /
• 2023

In this study, a recurrent neural network (RNN) was employed as a methodological approach to classify dolphin click signals derived from ocean monitoring data. To improve the accuracy of click signal classification, the single time series data were transformed into fractional domains using fractional Fourier transform to expand its features. Transformed data were used as input for three RNN models: long short-term memory (LSTM), gated recurrent unit (GRU), and bidirectional LSTM (BiLSTM), which were compared to determine the optimal network for the classification of signals. Because the fractional Fourier transform displayed different characteristics depending on the chosen angle parameter, the optimal angle range for each RNN was first determined. To evaluate network performance, metrics such as accuracy, precision, recall, and F1-score were employed. Numerical experiments demonstrated that all three networks performed well, however, the BiLSTM network outperformed LSTM and GRU in terms of learning results. Furthermore, the BiLSTM network provided lower misclassification than the other networks and was deemed the most practically appliable to field data.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2016.05a
• /
• pp.255-256
• /
• 2016

어선의 어업별 밀집 분포도 구축을 통해 어선의 통항흐름을 인지하여, 스크류/추진기 등의 손상과 어망 손괴사고 등을 예방할 수 있다. 아울러, 전국 연안 VTS의 관제구역 설정, 제주연안 돌고래 보호구역 설정, 해상풍력발전 단지 조성과 같은 해상교통안전진단 등의 타당성 입증자료, 허베이스피리트호 사건과 같은 유류유출사고 등과 같은 피해액 산출 추정을 위한 기초 자료로도 활용될 수 있을 것으로 판단된다.

• Proceedings of the Korean Society of Fisheries Technology Conference
• /
• 2003.10a
• /
• pp.75-78
• /
• 2003

고래류의 자원은 국제포경위원회(IWC)의 국제포경규제협약(ICRW) 의해서 1986년부터 상업포경업이 금지된이래 현재 전 세계적으로 꾸준히 증가되어, 최근 우리나라 연근해에서도 수년전까지만 해도 자취를 감추었던 고래류가 빈번히 출현하고 있으며, 특히 서해안에 상괭이군 동해안에 밍크고래군, 제주도 연안에 4월에서부터 9월 사이에 큰돌고래군이 유영하는 모습을 자주 볼 수가 있었다. (중략)